Here you are looking to solve for the unknown variable, y. To do so, you want to isolate this variable to one side of the equation in a way in which the equation will be in the form of " y = " .
Notice that the left hand side of the equation is in the form of a fraction. Since you are dividing y by 4, you are essentially multiplying y by 1/4. That is, y/4 = 2 ==> (1/4)y = 2
So, to solve for y, multiply both sides of the equation by the reciprocal of 1/4, which is 4/1 (or, 4). This will isolate the y, thus solving for it.
(1/4)y = 2
(4) * (1/4)y = 2 * (4)
(4/4)y = 2*4
y = 8